The present invention relates to a process for the quantitative detection of aliphatic nitroamines and nitroaromatics in liquid samples. It particularly relates to a liquid chromatography method for the quantitative determination of aliphatic nitroamines and nitrated aromatics in liquid samples, such as waste water samples.
The development of a rapid and quantitative method for the determination of trace quantities of aliphatic nitro-amines and nitroaromatics in aqueous effluent streams has recently become necessary as a result of an increasing concern for the presence and fate of munitions-related materials in the environment. Compounds of such as 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 2,4,6-trinitrotoluene (TNT) are typical members of these classes of explosive materials, and represent a significant portion of the munitions currently being produced in the United States. The occurrence of these and related materials in the environment is primarily a result of the discharge of aqueous process streams utilized during the synthesis of these compounds into the environment.
Heretofore, the prior art has developed many methods for the compositional analysis and for the determination of the purity of explosive mixtures. Typical examples of these prior art analysis methods include infrared spectroscopy, thin layer chromatography, and liquid chromatography. While these methods have proven adequate in the compositional analysis of nitrated explosives, the low sensitivities thereof preclude the use of such methods in the detection of trace quantities of these compounds, such as are involved in environmental analysis. Due to its much higher sensitivity, gas chromatography has therefore been used almost exclusively for the determination of trace levels of explosives. However, the gas chromatography analysis method is only suitable for use with those nitro-compounds which are relatively volatile at the temperatures employed therein. Since many aliphatic nitro-amines, nitroaromatics, and other nitrated compounds are non-volatile at these temperatures, gas chromatography is suitable for the detection of only a limited portion of these compounds. This inability to analyze many of the nitro munitions thus renders gas chromatography unsuitable for use in environmental analysis.
Moreover, it is an objective of any analysis procedure to limit sample losses to a minimum in order to insure accuracy of measurement. One of the principal sources of sample loss is due to the sample manipulation required in the analysis procedure. Due to the extensive sample manipulation necessary in gas chromatography, significant amounts of the nitrated compounds present in the sample are lost to thermal and photolytic degradation. Consequently, not only is the applicability of gas chromatography limited to a small group of compounds, but the results obtained thereby have a low and undesirable accuracy. Additionally, in order to maximize accuracy it is desirable that the chosen method of analysis should have the ability to detect any degradation products resulting from decomposition of the sample. With gas chromatography, as has been aforementioned, the ability to detect such degradation products is limited to those which are volatile at the temperatures employed therein.
Accordingly, in view of the large importance of nitrated compounds, and particularly the nitrated explosives TNT, RDX, and HMX, and the large concern for the existence of these compounds in the environment, there exists a great need in the art for a rapid and accurate method for quantitatively detecting trace quantities of these contaminants in liquid samples.